The Chemotherapy of Infectious Diseases Caused by Protozoa and Bacteria

The possibility of combating infectious diseases with chemotherapeutically active substances depends to a large extent on the structure of the pathogenic organism. Apart from the cure of contagious pleuro-pneumonia in horses with neosalvarsan, we have, as yet, no chemotherapeutic substance which is active in virus diseases. The position is scarcely better when we turn to bacterial infections due to cocci and bacilli. These two types of infective organisms occupy the lowest level in the scale of micro-organisms. On the other hand, the spirochætes, which also belong to the bacteria group, and, still more so, those causal organisms belonging to the protozoa, represent relatively highly differentiated species, and the more highly developed a pathogenic organism is, the more points for attack it appears to offer to the action of chemotherapeutic substances. It is, therefore, not to be wondered at that the best results with chemotherapeutically active substances have been obtained in spirochætal diseases (syphilis, relapsing fever, frambœsia, etc.), and above all, in protozoal diseases. There is scarcely a protozoal disease of man which cannot be cured nowadays by early treatment with the appropriate synthetic drug. (Sleeping sickness, malaria, amœbic dysentery, leishmaniasis.) Epizootics resembling human diseases, as for example, trypanoses, are also relatively easily dealt with by the same drugs as have been found of value in the treatment of disease in man. On the other hand, there has been a lack of success, up to the present, in the treatment of those diseases of animals which are not generally related to the tropical diseases of man. The most important of these epizootics are the piroplasmoses, which are caused by babesiæ and theileriæ and which are found, not only in tropical and subtropical regions, but also in temperate zones. In this paper the discovery of a new remedy against piroplasmosis will be reported (acaprin). Further, advice will be given of a new class of substances, which have an actual chemotherapeutic action in streptococcal infections (prontosil, prontosil S), so that one can hope to be able in the future also to attack bacterial infections due to cocci chemotherapeutically.